22nd–25th June, 2015 Kraków The First Evidence of Trace Fossils in Upper Eocene Sediments of Tbilisi Environs (The Achara –Trialeti Fold-Thrust Belt, Georgia) and Their Geological Significance Tamar Beridze, Zurab Lebanidze, Kakha Koiava, Rusudan Chagelishvili, Sophio Khutsishvili, Nino Khundadze

Ichnology as an important tool in solving of fundamental geological problems is still poorly comprehensible field of study in Georgia. Only rare references on findings of trace fossils are found in Georgian geological literature, where they are defined as general characteristic features of flysch sediments (hieroglyphs/bioglyphs or fucoids), and lack any type of precise definition, classification and geological interpretation. During the last decade based on the authors’ rich data from personal field observations, trace fossils were widely recorded in the Mesozoic-Cenozoic sedimentary basins of Georgia, mostly affected by turbiditic sedimentation (‘flysch’ basins).Accordingly establishing of fundamental integrated ichnological- sedimentological studies in Georgia has become a matter of great scientific importance

Madneuli tube worm fossils(C.T.S.Little et al.2007)

Paleocene-Lower Eocene Borjomi Flysch (The Achara –Trialeti Fold-Thrust Belt) The present study is one of the first attempts of identification and interpretation of recently found trace fossils in Upper Eocene suites of Tbilisi environs.

Georgia is situated between the still converging Eurasian and Africa-Arabian lithosphere plates, within a wide zone of continent-continent collision and serves as a connecting link between the European and Asiatic segments of the Alpian- Hymalaian orogenic belt.

Tectonic map of Georgia (Adamia et al.,2011 )

Generalised and simplified lithostratigraphic columns of the pre-collisional units of the Achara-Trialeti: west (a) and east (b) basins(Adamia et.al.,2011) Geological Map of Georgia(Adamia et.al., 2004 )

Arch Part of the Lisi Anticline

isp. Rhizocorallium isp.

Zoophycos isp.

.Regional stratigraphy In contrast to Upper Eocene Tbilisi suite, Oligocene sediments of Lisi anticline are free of biogenic sedimentary structures. This fact supports a supposition that during deposition of Maikop series (Oligocene-Lower Miocene) the bottom of the basin was saturated by H 2 S (hydrogen sulfide) and therefore was an unfavorable habitat for benthic communities. The nature of the rocks of Maikop series refers to significant changes of environment. The Mediterranian type ‘nummulitic’ sea was replaced by the Black Sea type basin where the bottom lacks any kind of life and only in the upper parts of the ‘sea’ are present fishes. As Upper Eocene and Oligocene suites of the Lisi anticline are lithologicaly almost similar, ichnological analysis will be a helpful tool in solving of a boundary problem between them. Different researchers drove the boundary on different levels and therefore the error in some cases reached several hundred meters. We consider that the boundary line could pass above the upper bedding planes of the youngest bioturbated beds. This will be a significant challenge from the regional stratigraphic point of view. Upper Eocene Tbilisi suiteOligocene-Lower Miocene Maikop series

 Lisi ichnofauna is interesting for paleogeographic reconstructions as well. There’s lithological evidence that at the end of the Upper Eocene the structures developed to the north and south from Lisi anticline (accordingly Mtskheta, Mamadaviti and Teleti anticlines) existed in terrestrial conditions. These anticlines, which already exsisted in the Middle Eocene, during late Eocene were still developing, were uplifted and eroded. Conglomerate units in the both flanks of these anticlines which comprise products of Middle Eocene rocks’ erosion transported from the uplifted parts of these anticlines confirm this opinion. In case of Lisi anticline we don’t have such criteria though presence of coarsegrained sandstones in the Upper Eocene sediments of the Lisi anticline may refer to the same type conditions for this structure as well. Apparently the Lisi anticline was not developed enough to undergo significant erosion. Even today it is less uplifted than mentioned above structures and the same picture we had in Late Eocene.  Existence of Rhizocoralliums characteristic to shallow water environments makes us to consider that to the west from their finding place in the central uplifted part of Lisi anticline terrestrial conditions were developed. The discovery of the relics of Lower Oligocene terrestrial mammalians in the Lower Oligocene sediments of the southern flank of the Lisi anticline confirms this opinion. This consideration needs further detailed studies aiming the correct analysis of the sedimentary basin.

Thank You